Give at least two ways to know if a reaction is endothermic or exothermic

Oxidation state of iron in mohrs salt

How has the scientific community addressed the safety of chemicals? a. chemicals are repeatedly tested, even those that have existed for a long time. b. existing chemicals are tested if they have never been tested before. c. chemicals are tested if they are suspected to have caused a problem. d. only new chemicals are tested.

Brainliesttt me asap! the below reaction can be categorized as more than one type of reaction. which reactions are these, and what are the types of reactions?